The present invention relates to an actuator assembly for maintaining and linearly positioning a magnetic head. More particularly, it relates to a non-frictional linear actuator assembly for fine positioning of a magnetic head, especially for use in a tape drive.
The use of magnetic tapes or disks to record, store and retrieve data is highly prevalent in today""s society. In general terms, the same magnetic principles apply to data storage on both magnetic tapes and disks. Namely, one or more magnetic recording heads are employed to record and retrieve data onto tracks formed along the tape or disk media. To this end, tape drive and disk drive manufacturers continually strive to improve upon the mechanisms utilized to accurately position and maintain the magnetic recording head relative to the track in question.
With specific reference to tape drives, a storage tape is driven along a tape path so as to interface with a magnetic head element having one ore more magnetic recording heads. A positioning mechanism is typically employed to transversely position the head with respect to the tape path (or the width of the storage tape) so as to enable recording and playback of any of a plurality of parallel tracks formed along the storage tape. Normally, a coarse positioning device, such as a stepper motor, a lead screw driven by the stepper motor and a head-mounting slide engaged with the lead screw, aligns the magnetic head element relative to a desired track Advances in the magnetic tape media technology has greatly increased data capacity by narrowing the width of individual tracks, thereby increasing the total number of available tracks on the storage tape. Head technology has correspondingly improved to accommodate and properly interact with the now more narrow tracks.
Generally speaking, coarse positioning devices are able to accurately index the head element transversely relative to the tape path. This indexing is based upon an assumed position of the storage tape relative to the head element. In this regard, every effort is made to precisely and consistently position the storage tape relative to the head element. Unfortunately, however, variations in tape position during tape transport is unavoidable. For example, tape edge variations, environmental thermal expansion and contraction, formatting inaccuracies, etc., invariably occur, leading to inadvertent transverse tape movement. For a narrow track storage tape, even a minute transverse displacement may cause a head tracking error.
To compensate for transverse displacement of the storage tape during use, tape drive systems commonly include a closed loop servo-tracking system whereby one of the tracks associated with the storage tape serves as a servo-track. The magnetic head designated to follow the servo-track essentially xe2x80x9cmonitorsxe2x80x9d the transverse position of the servo-track, and thus of the storage tape. The tracking system evaluates this transverse position information and, where necessary, transversely maneuvers the magnetic head element in a corresponding fashion. To this end, coarse positioning mechanisms are unable to instantaneously maneuver the magnetic recording head, and therefore are unacceptable with high-density tape applications. Instead, an additional fine positioning mechanism must be incorporated into the tape drive.
A variety of different fine positioning mechanisms or actuators have been envisioned. For example, it has been proposed to combine a stepper motor as a coarse positioner with a linear voice coil motor acting as a fine track positioner. The mechanism associated with the voice coil is typically complex, and rely upon one more springs, levers, cams, etc. to instantaneously maneuver and maintain the head element in response to energization of the voice coil as part of a closed servo-loop system. In this regard, existing fine positioning mechanisms are not rigid in all axes other than the desired linear axis, and therefore require additional frictional devices (such as bearings, etc.) to rigidly support the head element. Without this rigidity, non-linear articulation of the head element may occur, leading to undesirable tracking errors.
The technology associated with magnetic data storage continues to evolve. With respect to magnetic tape systems, these enhancements have placed a great emphasis on the ability to precisely position and re-position the head element relative to data tracks on the associated storage tape. Existing positioning or actuator technology may have certain drawbacks, and are relatively expensive. Therefore, a need exists for a magnetic head linear actuator assembly that is rigid in all axes other than the desired linear axis on a cost-effective basis.
One aspect of the present invention provides a magnetic recording head element linear actuator assembly. The actuator assembly includes a base, a platform, a core, a coil, a plurality of slats and a plurality of magnetic bars. The platform is positioned opposite the base and is configured to maintain a magnetic head element. The core is disposed between the base and the platform such that a space is defined between the core and the platform. The coil is wound about a central axis of the core. The plurality of slats maintain the platform relative to the base. In this regard, the plurality of slats are each deflectable from a straightened state, and are biased to return to the straightened state following deflection. Finally, the plurality of magnetic bars are secured to respective ones of the plurality of slats adjacent the coil. With this configuration and during use, a magnetic field generated by the coil induces deflection of the plurality of slats via the magnetic bars, thereby causing the platform to move linearly toward the base. In one preferred embodiment, a central passage is formed through the platform, core, and base, and is sized for assembling the linear actuator assembly to a coarse positioning mechanism, such as a lead screw. In another preferred embodiment, the coil and the magnetic bars are centrally positioned relative to the base and the platform.
Another aspect of the present invention relates to a tape drive for recording data on, and reading data from, any one of a plurality of parallel data tracks extending along a length of magnetic storage tape with a magnetic head element adapted to interface with the tape along a tape transport path and to be variably positioned transversely relative to the tape transport path. The tape drive comprises a magnetic head element and a fine positioning, linear actuator assembly. The linear actuator assembly maintains the magnetic head element at an interface position with the storage tape and maneuvers the magnetic head transversely relative to the tape transport path. In this regard, the actuator assembly includes a base, a platform, a core, a coil, a plurality of slats and a plurality of magnetic bars. The platform is positioned opposite the base. The magnetic head element is secured to an outer surface of the platform. The core is disposed between the base and platform such that a spacing exists between the core and an inner surface of the platform. The core is wound about a central axis of the core. The plurality of slats rigidly maintain the platform relative to the base. Further, the plurality of the slats are each deflectable from a straightened state, and are biased to return to the straightened state following deflection. Finally, the plurality of magnetic bars are secured to respective ones of the plurality of slats adjacent the coil. With this configuration, a magnetic field selectively generated by the coil induces deflection of the plurality of slats via the magnetic bars. Upon deflection, the platform and the attached magnetic head element are caused to move toward the base, transversely relative to the tape transport path. In one preferred embodiment, the tape drive further includes a servo-controller electrically connected to the magnetic head element and the coil. With this configuration, the servo-controller prompts current delivery to the coil commensurate with a deviation in transverse tape positioning as otherwise sensed by the magnetic head element.